An Adjuvant-Free Mouse Model Using Skin Sensitization Without Tape-Stripping Followed by Oral Elicitation of Anaphylaxis: A Novel Pre-Clinical Tool for Testing Intrinsic Wheat Allergenicity

Abstract

Wheat is a major food allergen per the regulatory bodies of various nations. Hypersensitivity reactions to wheat have been steadily increasing for reasons that are not completely understood. Wheat-allergy models typically use adjuvants to induce sensitization to wheat proteins followed by an intraperitoneal challenge to elicit anaphylaxis. Although these models are very useful, they lack the ability to reveal the intrinsic allergenicity potential of wheat. To improve the mouse model of wheat allergy, we tested the hypothesis that repeated skin application of salt-soluble protein extract (SSPE) from durum wheat will clinically sensitize the mice to oral anaphylaxis to SSPE. Balb/c mice were bred and maintained on a plant-protein-free diet and used in the experiments. Adult female mice were exposed to SSPE once a week for 9 weeks via a solution on intact skin. Sensitization was measured by SSPE-specific IgE (sIgE) antibody and total IgE (tIgE) levels. Oral anaphylaxis was quantified by hypothermic shock response (HSR), and mucosal mast cell response (MMCR) was quantified by measuring MMCP-1 after oral challenge. Using single mouse data, correlation analyses were performed to determine the relationship among the allergenicity readouts. Spleen cytokines were quantified using a protein microarray method. Our results show that (i) repeated skin exposures to SSPE elicited robust increases in the sIgE and tIgE levels; (ii) skin exposure to SSPE was sufficient to sensitize mice for oral anaphylaxis and MMCR; (iii) both HSR and MMCR showed a strong correlation with each other, as well as with sIgE, and a modest correlation with tIgE levels; (iv) selected Th2/Th17/Th1 cytokines were elevated in skin-sensitized mice; and (v) oral allergen-challenged mice showed selective elevation of IL-6 and a panel of chemokines compared to saline-challenged mice. Together, we report the development and characterization of a novel adjuvant-free wheat-allergy mouse model that uses skin sensitization without tape-stripping followed by oral elicitation of anaphylaxis. Furthermore, validation of quantifiable wheat allergenicity readouts makes this model particularly suitable as a pre-clinical testing tool to assess the intrinsic sensitization/oral-anaphylaxis elicitation potential of novel wheat proteins (e.g., processed wheat) and to develop hypo/non-allergenic wheat products.

Diagnostic management of patients reporting symptoms after wheat ingestion

“…After 9 weeks, the researchers elicited robust increases in wheat-specific IgE (sIgE) levels and anaphylaxis following oral administration of wheat. This research clearly demonstrates the power of wheat as a food allergen ( 54 ). It also supports the dual-allergen exposure hypothesis for the development of food allergies in a mouse model.…”

Intrinsic Allergenicity Potential of Salt-Soluble Protein Extracts from the Diploid, Tetraploid and Hexaploid Wheats: Validation Using an Adjuvant-Free Mouse Model

“…We used the sIgE data from the above validation studies and our previously reported durum wheat study [ 33 ] for preparing a comparative sensitization map. The sIgE antibody levels elicited by respective wheats were determined by subtracting the baseline (pre) sIgE levels from the 8th response (8R) sIgE levels.…”

“…We used the absolute changes in the rectal temperature data upon oral allergen challenge from the above validation studies of T. monococcum , T. aestivum and Ae. tauschii wheat and our previously reported durum wheat ( T. durum ) studies [ 33 ] for preparing a comparative disease elicitation map. Figure 11 A,B show the disease elicitation potential map at 15 and 20 min post oral allergen challenge with a 15 mg SSPE dose.…”

“…Several animal models have been reported in the literature to study wheat allergenicity [ 27 , 29 ]. We recently reported a novel adjuvant-free transdermal sensitization followed by oral elicitation (TS/OE) mouse model of wheat allergy using T. durum [ 33 ]. The TS/OE mouse model is uniquely suited for testing the intrinsic allergenicity potential of genetically distinct wheats because it does not use adjuvants for inducing sensitization to the wheat allergen [ 33 ].…”

“…We recently reported a novel adjuvant-free transdermal sensitization followed by oral elicitation (TS/OE) mouse model of wheat allergy using T. durum [ 33 ]. The TS/OE mouse model is uniquely suited for testing the intrinsic allergenicity potential of genetically distinct wheats because it does not use adjuvants for inducing sensitization to the wheat allergen [ 33 ]. Here, we validated the TS/OE model for three other wheat species [hexaploid common wheat ( Triticum aestivum ) , diploid einkorn wheat ( Triticum monococcum ), and the ancient diploid wheat progenitor, Aegilops tauschii ], and then tested the hypothesis that the SSPEs from wheat species will exhibit differences in relative allergenicities.…”